1. Field of the Invention
The present invention relates to a quick disconnect coupling used for connecting pipes and, more particularly to a quick disconnect coupling of the self-locking type.
2. Description of the Prior Art
The interlocking action in a quick disconnect coupling is commonly provided by a set of balls annularly disposed and received with a suitable clearance into recesses, provided in a cylindrical sleeve of the female portion, said balls cooperating with a groove of the male portion, the side faces of which forming ramps, so that when the male portion is introduced into the female portion, said balls are first moved radially towards the outside by a ramp of said groove of the male portion, and are then resiliently urged into a groove having a suitable contour formed into the peripheral surface of the male portion.
In such a type of quick disconnect coupling, the radial movement of the balls is generally controlled by a surrounding collar slidably received onto said sleeve containing the balls therein, said collar being formed with a ramp which connects two axial bores of different diameters formed into said collar, so that in a first position of said collar, the bore having the smaller diameter surrounds the recesses where the balls are received and prevents said balls to move radially towards the outside, and in a second position of said collar, the bore having the larger diameter surrounds the recesses where the balls are received, thus permitting the balls to move radially towards the outside, the ramp connecting said two bores acting, to move the balls back towards the centre of the female portion.
The radial movement of said balls is thus controlled by an axial movement of the locking collar.
This collar is generally biased by a strong compression spring which tends to press the collar against a shoulder counterbored into said cylindrical sleeve. In this first position of said collar, or nonoperative position, the bore having the smaller diameter in said collar surrounds the balls so that they are maintained in their retracted or inner position.
Therefore, a quick disconnect coupling of the above type is operated as follows:
- the locking collar is slid to its unlocking position and maintained in this position while introducing the male portion into the female portion. When said male portion is fully introduced into the female portion, the locking collar can be released, the return spring moving same back to its first or rest position, thus locking the balls and hence the male portion into the female portion. PA1 - the male portion being held in one hand, the female portion being held in the other hand, simultaneously, the moving part of the female portion, i.e. the locking collar, must be slid as above mentionned while the rest of the coupling must be held stationary with said other hand. For small size couplings this sliding action of the collar is generally achieved with two or three fingers. But, for larger size couplings, the locking operation becomes all the more difficult as the collar return spring is generally very strong.
The female portion, which supports the locking collar is generally connected to a nonsupported flexible pipe or hose so that when the quick disconnect coupling has to be connected, the following problem arises:
The result of this difficult handling for connection is that, in most instances, a part of the effort applied on the locking collar is transmitted to the pipe which is connected to the female portion of the coupling, thus causing stresses in the pipe connection and resulting in pipe failure or shearing.
This problem is further aggravated when a quick disconnect coupling fitted with a check valve is being used, that is when the pipe connected to the female portion is under pressure. In this case, in addition to the efforts normally applied to the female portion of the coupling, must be added the force to be exerted by the male portion to lift the check valve, and eventually to move the corresponding seal, to overcome the forces created by the fluid under pressure and the check valve return spring.